With rapid advancement of the fabrication technology of a thin film transistor liquid crystal display (TFT-LCD), the LCD is largely applied in various electronic products such as a Personal Digital Assistant (PDA) device, a notebook computer, a digital camera, a video camera, and a mobile phone due to the fact it has advantages of smaller size, less weight, lower power consumption and low radiation. Moreover, the quality of the LCD is ceaselessly improved and the price thereof is continuously decreased since manufacturers aggressively invest in research & development and employ large-scale fabricating equipment. That promptly broadens the applied fields of the LCD.
In the fabrication of the TFTs or related circuits, thin film deposition and photolithography processes are repeatedly performed on a substrate to define corresponding devices and circuit patterns. A variety of insulating films or conducting layers are formed on the substrate by chemical vapor deposition (CVD) or physical vapor deposition (PVD) procedures, and the desired devices are fabricated or the related circuits are defined by photolithography processes to pattern various types of thin films into a desired shape. In a typical photolithography process, a photoresist is first coated on a substrate. An exposure procedure is then performed using a photo mask having a certain pattern to have the photoresist film on the substrate selectively sensitized such that the pattern of the photo mask can be completely transferred onto the photoresist film. Thereafter, the photoresist film is developed. Based on the characteristics of the material used for the photoresist, the exposed portion or the unexposed portion of the photoresist film is selectively removed to form a resist pattern. Afterwards, the underlying film is selectively etched using the resist pattern as an etch mask to pattern the film. Hence, the related device is fabricated.
A spin coating procedure is typically used to coat a photoresist film. When the liquid of photoresist is sprayed onto the substrate, the substrate is simultaneously rotated so that the photoresist film coated on the substrate can be formed more uniformly. However, during such a spin coating, the photoresist liquid would flow to the edges of the substrate due to the centrifugal force produced by rotation of the substrate and then, the photoresist materials attach to the edges, sidewalls and even the bottom surface of the substrate. When a robotic arm or a carrying base in the subsequent processes are contacted with the substrate, the attached photoresist materials might peel off to cause serious particle pollution.
To solve this problem, an edge removing procedure is performed after the photoresist film is coated so that the photoresist materials attached to the edges, sidewalls and the bottom surface of the substrate can be removed. During edge removing, referring to FIG. 1, edge removing arms 10 extended from an edge remover are distributed at the four corners of a substrate 12 and go around clockwise or counterclockwise along the edges of the substrate 12 so as to get rid of the photoresist materials attached to the edges of the substrate 12 and to keep the photoresist 14 at the interior of the substrate 12.
FIG. 2 is a schematic perspective diagram of the construction of the edge removing arm 10, which includes a flat plate 20 and a L-shape board 22. The flat plate 20 is combined to the L-shape board 22 to form a recess for receiving the edge of the substrate 12. An upper immovable arm 24 whose rear end is connected with a conduit 26 carrying a chemical solvent, is mounted on the top surface of the flat plate 20 to deliver the chemical solvent through a nozzle (not shown) at the bottom surface of the flat plate 20 to spray over the top surface of the substrate 12. A lower immovable arm 28 whose rear end is also connected with a conduit 30 carrying a chemical solvent, is mounted on the bottom surface of the L-shape board 22 to deliver the chemical solvent through nozzles at the top surface of the L-shape board 22 to spray over the bottom surface of the substrate 12. Moreover, a pedestal 32 is combined to the rear ends of the flat plate 20 and the L-shape board 22. A vacuum conduit 34 goes through the pedestal 32 and the L-shape board 22 in order to pump air from the recess through an opening at the wall of the upright portion of the L-shape board 22.
FIG. 3 is a partially schematic sectional view of the construction of the edge removing arm 10. As mentioned in the above, in the edge removing procedure, the edge of the substrate 12 is inserted to the recess constructed by the flat plate 20 and the L-shape board 22. After the vacuum conduit 34 is activated to pump air from the recess, the chemical solvents carried in the conduits 26 and 30 are respectively sprayed over the top and bottom surfaces of the substrate 12 respectively through the nozzles 36 and 38 so as to remove the photoresist materials attached to the edge of the substrate 12. The chemical solvents on the surface of the substrate 12 and the dissolved photoresist particles are simultaneously pumped out through the vacuum conduit 34 so as to prevent the chemical solvents from flowing into the other locations on the substrate 12 to erode the portion of the photoresists desired to remain on the substrate 12.
However, whenever the pump module of the vacuum conduit 34 cannot provide sufficient suction or has intermittent breakdowns, the chemical solvent sprayed out from the nozzle 36 of the flat plate 20 would splash onto the interior of the substrate 12, as shown by the dotted arrow in FIG. 3, to erode the portion of the photoresists desired to remain on the substrate 12. This causes the subsequent defined patterns not to be precise and reduces the yield of the entire process. Particularly, with shrink in the device size and increase in the integration, a slight error in patterns might lead to operation failure of a large number of devices. Therefore, under the requirement to maintaining the original design of the current edge remover, how to effectively solve the problem of solvent splashing during edge removing has become an important subject so as to further enhance the yield of product fabrication.